1. Field of the Invention
The present invention relates to a semiconductor device in which a semiconductor chip is mounted on a lead frame, and bonding pads on the semiconductor chip and leads of the lead frame are electrically connected by bonding wires.
2. Description of the Related Art
A semiconductor chip having a ball grid array (BGA) structure using a semiconductor chip on which all pads are arranged along only one side of the chip is described, e.g., on pages 4 and 5 and FIG. 1 of Jpn. Pat. Appln. KOKAI Publication No. 2001-102515. In this semiconductor device, a semiconductor chip having a plurality of pads formed on only one side of the chip is prepared, and this semiconductor chip is stacked, as it is slightly shifted, on another semiconductor chip. This reduces the package size and facilitates wire bonding.
However, the following problem arises if a semiconductor chip having a plurality of pads formed only on one side of the chip is applied to a semiconductor device having a TSOP (Thin Small Outline Package) structure.
In the TSOP-structure semiconductor device, a semiconductor chip is fixed on die pads of a lead frame via an insulating adhesive. Also, a pair of inner lead groups of the lead frame and pads on the semiconductor chip are electrically connected by bonding wires. If a semiconductor chip having pads formed only on one side of the chip is used, one inner lead group is close to the pads, and the other is far from them. The bonding wire length extremely increases when the inner lead group far from the pads is connected to them by bonding wires. Therefore, in a resin encapsulation step performed later, the wires are readily carried away by a resin. Adjacent wires are likely to undergo short-circuiting.
Jpn. Pat. Appln. KOKAI Publication No. 2001-217383 discloses a semiconductor device that comprises a substrate and two identical semiconductor chips. Each chip has bonding pads provided on one edge of a major surface. The chips are laid, one upon the other, on the substrate. The chips are oriented in the same direction, and the bonding pads of one chip are therefore located near those of the other chip.